Method of controlling wax sweating



Patented Aug. 20, 1946 f f UNITED STATES PATENT OFFICE :METHOD OFCONTROLLING W SWEATING Seymour W. Ferris, Mount Holly, N. J., assig'norto The Atlantic Refining Company, Philadelphia, lra., a corporation ofPennsylvania Application octber 19, 1942, serial No. 462,653

' 7 claims. (c1. 19e-'20) 1 Y The present f'invention relates VVto thesweating of oily wax to reduce the oil content thereof, and relates moreparticularly to improvements in controlling the sweating of such wax.

An object of this invention is to control wax sweating in such a manneras to produce high yields of wax of reduced oil content withoutsubstantial loss of desirable wax in the sweat oil.

` A further object of this invention is the appli-- 'products of reducedoil content. For example,

a commercial product such as scale wax contains from 8% to 10% of oil,whereas fully rened paraflin wax contains less than about 4% ofoil, andhigh tensile strength parain wax contains less than 1.5% of oil, all ofthe oil contents being determined by treatment with ethylene dichlorideas described more fully hereinafter.

Heretofore, in the sweating of oily wax, it has been very diiicult tojudge when the oil has been completely removed, or removed to thedesired extent, from the wax remaining in the sweating pans. Thisdiiculty arises from the fact that it is practically impossible toobtain a sample representative of all of thewax remaining in thesweating pans, and in addition, the determination of the oil content ofthe sweated wax by a selective solvent method is time-consuming. Whenmore than one cycle of sweating is employed for the production of afullysweated wax, there is a greater likelihood that the nal product will besubstantially oil-free, but when single cycle sweating is carried out,the determination of the proper time to terminate the sweating becomesmore important, since stopping too soon results in incomplete oilremoval and low tensile strength, and if each run is carried far enoughto insure the lproduction of high tensile strength wax, the averageyield of the wax will be reduced.

It has been found that one of the most distinctive properties of a waxis the relationship between its melting point and its refractive index.measured at some temperature above its meltexperimentally sweated wax.

ing point. For convenience, the `melting `point is determined inaccordance with A. S. T. M. Method D87-37 Melting point of paraliin wax,and the refractive index is measured at 176 F. in a suitablerefractometer.

In accordance with the present invention, use is made of therelationship of the melting point and refractive'index of the sweatedwax and the sweat stream in controlling the duration of the sweatingoperation. More specifically, a sample of an oily wax is experimentallysweated by slowly raising the temperature of the mixture, and successivesamples of the material sweated from the mixture, i. e., the sweatstream, are taken. The meltingl point, refractive index, and oil contentof each of the samples is determined, and the oil content of the sweatedwax may also be determined at each interval at which a sweat streamsample is taken. YFrom the'refractive index-melting point relationshipof the sweat stream samples and the oil contents of the sweat stream andsweated wax samples, it is thus possible to determine experi-mentallythe point Vat which sweating should be stopped in order to obtain a nalwax having a desired oil content. The results thus determinedexperimentally for a given wax stock may then be applied directly to thecontrol of a large scale commercial sweating operation. For example, agiven wax stock is sweated on large scale and successive sweat streamsamples are taken. The melting point and refractive index of each sampleis determined as rapidly as the sample is taken from the sweat stream.When the refractive index-melting point relationship of a sweat streamsample is found to correspond to an experimentally determined valueindicating a known oil content in the experimentally sweated wax orsweat stream sample, the large scale sweating operation is stopped andthe resulting sweated wax will be found to have, substantially the sameoil content as the Thus, by simply determining therefractiveindex-melting point relationship of a sweat streamV samplefrom a commercial sweating oven and comparing it with the refractiveindex-melting point'relationship of sweat stream samples predeterminedexperimentally for sweated wax of'known oil content, it isy possible tocontrol closely the large scale sweatingiof wax and to stop the sweatingat ex; actly the proper time so that the wax is neither under-sweatednor over-sweated. Since the refractive index and melting point of thesweat `stream samples are easily and rapidly deterthe refractive indexand melting point for sweat Manufaturing Company, the aurometer scalebeing calibrated from zero to 100. The 100 durometer reading indicatesno penetration, while thev zero reading indicates complete penetration.Tensile strength of thewax isgiven in lbs/square inch.

stream samples from a commercial slack wax, and the correlation of such-relationship with the oil'k content of the sweat stream samples and ofthe sweated wax.

Sweat stream Sweated wax Y Hardness R. I., P., Percent` P., PercentWeight per- Tensile 176 F. F. 'o F. oil cent yield strength E 111382 95`37.5 Y F 1 .4350 99 28 .5 G l .4291 109 14.9 Y:El: 1.4280 115 8.6 126.62.0 29.8 I -1 .4273 120 4.1 129 l .0 23 .2 30 0 132 J l .4275 127 .5 1.1 133 .5 0 .3 6 .3 90 30 378 Referring to the drawing, inwhich-refractive index is plotted against melting point, the lines ABand CD represent the limits within which lie the majority of thehydrocarbons present in substantially oil-'free waxes. The purestraightchain parain hydrocarbons will be foundV to lie along thelineAB, whereas the substantially Voilfree waxes may lie vanywhere withinthe area defined vby AB and CD. The equation for the line ABis.11.=`1.3950+.000242T, and the equation for the line CD isn=l.3793+.0004T, n being the 'refractive index at 176 F., and T beingthe A. S. T. M. melting pointfF.

, Upon the drawing is also plotted a curve defined by the points E, F,G, H, I, and J, representing Ythe refractive index-melting pointrelationships of successive sweat stream samples from an experimentallysweated vheavy paran slack wax having an initial oil content of 33.4% byweight and a melting pointof 106 F. The oil content of the slack wax,aswell asthat of the sweat stream samples and sweated wax, wasdetermined by the following method.

25 grams of oily wax is dissolved in ethylene vdi'chloride 'and madeupto 500 cc. at room temperature F.) the solution is then cooled with4'stirring to 5 F. and filtered at such temperature through rapidfiltering qualitativeY filter paper. The wax on the filter is thenthoroughly washed f with ethylene dichloride at 5 F., and an aliquotportion of the filtrate cc.) measured at room ene dichloride has beenremoved, in order to facilitate Vthe removal of the Ylast traces ofthesolvent. IThe oilv residue isweighed and multiplied Referring again tothe drawing, the constituents of a hydrocarbon wax, such asasubstantially oil-free parafn Wax, have refractive indexmelting pointrelationships which f all within Ythe area defined by the lines AB andCD. Liquid constituents of parain distillate, however, Vexhibitrelatively high refractive indices, and when the refractiveindex-'melting point relationship of the first sweat stream sample isfound to lie, for example, at point E, it is'mmediately known `thatconsiderable oil is present. When Ythe slackwax is subjected to furthersweating, however, the sweat stream shows progressively less oil Vandtherefore the points will be found to movev to the left as indicated atF, G, H, and I on the drawing.

rise, due to the increasing melting points, and

inasmuch as such samples areapproaching the composition of substantiallypure wax (point J Y'the pointsl will roughlyr parallel the line, 'When'such condition is reached, the wax remainingin the sweating pans issubstantially freeofV oil. For any particular waxstock, it maybedetermined experimentally how close the refractive index-meltingpointk value yof the sweat stream must approach the line AB before the'sweated by a factor to correct forV the aliquot portion of Y theethylene dichloride filtrate employed. I The corrected value Vis theweight per cent of oil inthe In the following table are given therefractive indices (R. 1.)', melting` points (M. P.)-,- and oil contentsfor the sweat stream samples E, F, G, H, I, and J as well as the meltingpoints, oil contents, yields, hardness, and tensile Vstrength for thesweated waxes whenthe sweating was stopped at points I-l, I, and J. Thehardness was determined b'y means of Aan instrument known as ladurometer supplied by the Shore Instrument .wax remaining'inthe pans isof desired quality.

Each wax stock has a particular curve of its own, and the position ofthe Vcurve on the accompanying drawing may change as either the vboilingrange or the sourceof the wax distillate, and therefore the wax stock,varies.

In order to produce from a slack wax stock having an oil content of from25% to 40% by weight, a commercial grade Vof scale wax having-an oilcontent of 8% to 10%, it has been found that the refractiveindex-melting point relationship of the sweat stream should fall. withinthe limits defined by lines. having the equations n=l.3998-|-.0'G0242Tand n=l.l00 3-{-.00O242T.

For the production of a fully. refined pi traii11 V wax the refractiveindex-melting point relationship of the sweat stream should fall withinthevlimits de ned by lines having-the equations I And for the productionof high tensile strength wax 'containing less than about 1.5% of oil,and preferably less than 1% of. oil, the refractive index-melting pointrelationship of the sweat 'stream should fall within the limits definedby lines having the equations n=1.3964-}-.O00242T and n=1.3969+.000242T.

In another aspect of the present invention, it has been found that therefractive index lof the sweat stream is, per se, a'valuable guide inindicating the point at which sweating should be terminated,particularly in the production of waxes of exceedingly low oil content,i. e., less than about 1% by weight of oil. By determining the minimumrefractive index of the sweat stream and then terminating sweating whensuch value is reached, the resulting sweated wax will contain little orno oil. Referring to the draw-v ing, it will be seen that the minimumrefractive index of the sweat stream is reached at a point between I andJ, and that the oil content of the sweated wax when the sweating wasstopped at I was about 1%. By terminating' the sweating at the minimumrefractive index between I and J, a somewhat higher yield of low oilcontent wax would be obtained than by continuing the indices and themelting points of successive sam- I ples of the sweat stream, andterminating the sweating of the wax when a sweat stream sample exhibitsa melting point higher than that of the 'preceding sample, and arefractive index at least as great as that of said preceding sample.

2. The method of reducing the oil content of oily Wax, which comprisessubjecting said oily wax to sweating, and terminating the sweating ofthe -wax when the refractive index of the sweat stream attains a minimumvalue.

3. The method of reducing the oil content of oily Wax, which comprisessubjecting said oily wax to sweating, and terminating the sweating ofthe wax when the relationship between the refractive index at 176 F. andthe melting point in F. of at least two successive samples of the sweatstream fall, on a plot of refractive index versus meltingpoint,substantially parallel to the line represented by the equationWhere n denotes the refractive index and T denotes melting point in 9F.l

4. The method of reducing the oil content of oily wax, which' comprisessubjecting said oily wax to sweating, and terminating the sweating ofthe wax when the relationship betweenk the refractive index at 176 F.and the melting point in F. of a sweat stream sample falls, on a'plot ofrefractive index versus melting point, Within the lines defined by theequations n=1.3964-|-0.0G0242T and n=l.4003|-0.000242T, where "nldenotes the refractive index `and T denotes melting point in F. w

5. The method of producing a high tensile wax, which comprisessubjecting an oily wax to sweating, and terminating the sweating of thewax when the relationship between the refractive index at 176 F. and themelting point in F, of a sweat stream sample falls, on a plot ofrefractive index; versus melting point, within the lines defined by theequations and n=1.3969+0.000242T, ywhere. n denotes the refractive indexand T denotes melting point in F.

6. The method' of producing a refined wax, which comprises subjecting anoily wax to sweating, and terminating the sweating of the wax when therelationship between the refractive indexat 176 F. and the melting pointin F. of a sweat stream sample falls, on a plot of refractive indexversus melting point, within the lines den=1.398 3+0.000242T, where ndenotes the refractive index and 'I'"` denotes melting point in F.

7. The method of producing scale wax, which comprises subjecting an oilywax to sweating, and terminating the sweating of thewaxwhen therelationship between the refractive index at 176 F. and the meltingpoint in F. of a sweat stream sample falls, von a plot of refractiveindex versus melting point, within the lines defined 'by the SEYMOUR W.FERRIS.

